This invention generally relates to television receiver tuning control systems and more particularly is directed to a control system for a channel/frequency band programmable television receiver tuner.
The increasing amount of pay television, subscription television (STV), cable television (CATV) and master antenna television (MATV) independent programming available for viewing has given rise to various attempts to limit viewer accessibility to these programs. For example, since an increasing number of television programs are available on a "pay-as-you-view" basis, the distribution of these programs necessarily involves an attempt to limit the availability of these signals to only paying customers. Such video signal distribution systems proposed in the past have typically employed such devices as signal scramblers and unscramblers, or systems controlled by coins, charge cards, tokens or similar articles to provide a special television programming capability. The latter systems generally involve program signals moving in one direction from the received signal input end to the remotely-located television receivers and control and monitoring information traveling in the opposite direction. The former systems generally require somewhat sophisticated signal processing devices while the latter systems necessitate the use of monitoring and control procedures and devices.
One example of a signal scrambling approach to limiting television signal distribution is disclosed in U.S. Pat. No. 4,057,827 to Morehead which makes use of a signal processing device at each remotely-located television receiver. Each signal processor includes a converter for converting the received signal from the standard channel to a locally unassigned VHF channel or one of the unused UHF channels. In addition to a signal converter, each control box also includes a digital encoder and timer, an RF transmitter, a channel program selector switch, and a coupler for feeding the RF transmitter signal output back through the television cable distribution system. Information containing the room number, channel being watched, and/or information is digital code modulated on an RF carrier and transmitted to the central processor receiver, demodulated, fed to the central processor, verified and stored for future use, including billing printout. While offering a highly automated signal distribution and monitoring system, this approach involves an additional, relatively expensive component in each room where the received television signal is to be viewed.
Another approach to selective television signal distribution is disclosed in U.S. Pat. No. 3,859,457 to Kirk wherein is described a selective video suppression apparatus including a band eliminating, notch filter nominally tuned to the channel viewing frequency spectrum. The attenuation of this filter is modulated at a rate faster than the automatic gain control (AGC) response of the television receiver with the result that the varying amplitude incoming signal supplied to the essentially fixed gain television receiver inhibits the receiver from displaying the incoming video signal due to a lack of vertical synchronization, lost color sub-carrier recovery and great amplitude intensity differences. Another approach involving the use of a band suppression filter is taught in U.S. Pat. No. 3,968,327 to Gregg wherein each television receiver has one or more band suppression filters barring reception of a corresponding channel signal. A control signal from a central control station is detected at the receiver and disables the filter at a selected receiver so that the program can be viewed. Both of the aforementioned approaches suffer from a limitation inherent in the use of any signal filtering scheme, i.e., signal losses and a general degradation of the received video signal.
The present invention is intended to avoid the aforementioned limitations by providing a selective video reception control system which is completely compatible with existing television signal distribution systems, is inexpensively incorporated in each individual television receiver and is particularly adapted for use in a hospital or hotel setting where it is desired to program each television receiver to receive only a limited number of frequency bands and only selected channels in each band.